#include<bits/stdc++.h>
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
#define pii pair<ll,ll>
#define rep(i,a,b) for(ll i=(a);i<=(b);++i)
#define per(i,a,b) for(ll i=(a);i>=(b);--i)
using namespace std;
bool Mbe;
ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
void write(ll x){
    if(x<0)putchar('-'),x=-x;
    if(x>9)write(x/10);
    putchar(x%10+'0');
}
const ll N=1009;
const ld pi=acos(-1);
ll n,m,cnt[N];
ld ans;
ll Dis(ll x,ll y){
    if(x<y)return min(y-x,2*m-y+x);
    return min(x-y,2*m+y-x);
}
bool Med;
int main(){
    cerr<<fabs(&Med-&Mbe)/1048576.0<<"MB\n";
    n=read(),m=read();
    //直线上
    rep(i,1,2*n+1){
        rep(j,i+1,2*n+1)ans+=abs(i-j);
    }
    if(m==1){
        rep(i,1,2*n+1)ans-=abs(n+1-i);
    }
    ans*=m;
    //同一个圆上
    rep(i,1,2*m){
        rep(j,i+1,2*m){
            if(i==j||abs(i-j)==m)continue;
            cnt[Dis(i,j)]++;
        }
    }
    rep(i,1,n){
        rep(j,1,m){
            ans+=cnt[j]*min(pi*j*i*1.0/m,(ld)i*2.0);
        }
    }
    cnt[0]+=2*m;
    rep(i,1,m)cnt[i]*=2;
    //不同圆之间
    rep(i,1,n){
        rep(j,i+1,n){
            rep(k,1,m)ans+=cnt[k]*(j-i+min(pi*k*i*1.0/m,(ld)i*2.0));
        }
    }
    cout<<fixed<<setprecision(10)<<ans;
    return 0;
}